Heretofore, a number of retroreflective sheeting products have been marketed. A typical example is characterized by a single layer of tiny optical elements embedded in a polymeric bead bond layer and in a polymeric spacing layer. The spacing layer is typically backed by a specularly reflective layer and an adhesive with a strippable protective layer (i.e., a release liner). The bead bond layer is typically surfaced with a top film. Retroreflective sheetings such as this are known as "embedded" lens sheeting (or often as "enclosed" lens sheeting). The first example of an embedded-lens sheeting was taught by U.S. Pat. No. 2,407,680 (Palmquist et al.). See also, for example, U.S. Pat. Nos. 3,551,025 (Bingham et al.), 3,795,435 (Schwab), 4,664,966 (Bailey et al.), 4,530,859 (Grunzinger, Jr.), 4,721,649 (Belisle et al.), 4,725,494 (Belisle et al.), and 4,808,471 (Grunzinger).
Certain of the bead bond layers described in these patents are tacky prior to final cure when the optical elements are applied and set, whereas others are nontacky. Some of the layers, including the bead bond layers, are made of polyurethanes, which may or may not be crosslinked. Such sheeting has been sold commercially for many years in large volume and to the general satisfaction of its users. Despite this general satisfaction, there has been a desire for an improvement in certain properties of the sheeting as technology advances and as decentralized manufacturing expands. For example, it is desired to produce retroreflective sheeting which has greater conformability and embossability, particularly under high speed embossing forces, than retroreflective sheeting heretofore known in the art.